Global Warming: Scientists Reveal Timetable

As present world temperatures are already 0.7C above the pre-industrial level, the process is well under way. In the near future - the next 25 years - as the temperature climbs to the 1C mark, some specialized ecosystems will start to feel stress, such as the tropical highland forests of Queensland, which contain a large number of Australia's endemic plant species, and the succulent karoo plant region of South Africa. In some developing countries, food production will start to decline, water shortage problems will worsen and there will be net losses in GDP.
It is when the temperature moves up to 2C above the pre-industrial level, expected in the middle of this century - within the lifetime of many people alive today - that serious effects start to come thick and fast, studies suggest.
Substantial losses of Arctic sea ice will threaten species such as polar bears and walruses, while in tropical regions "bleaching" of coral reefs will become more frequent - when the animals that live in the coral are forced out by high temperatures and the reef may die. Mediterranean regions will be hit by more forest fires and insect pests, while in regions of the US such as the Rockies, rivers may become too warm for trout and salmon.
In South Africa, the Fynbos, the world's most remarkable floral kingdom which has more than 8,000 endemic wild flowers, will start to lose its species, as will alpine areas from Europe to Australia; the broad-leaved forests of China will start to die. The numbers at risk from hunger will increase and another billion and a half people will face water shortages, and GDP losses in some developing countries will become significant.
But when the temperature moves up to the 3C level, expected in the early part of the second half of the century, these effects will become critical. There is likely to be irreversible damage to the Amazon rainforest, leading to its collapse, and the complete destruction of coral reefs is likely to be widespread.
The alpine flora of Europe, Australia and New Zealand will probably disappear completely, with increasing numbers of extinctions of other plant species. There will be severe losses of China's broadleaved forests, and in South Africa the flora of the Succulent Karoo will be destroyed, and the flora of the Fynbos will be hugely damaged.
There will be a rapid increase in populations exposed to hunger, with up to 5.5 billion people living in regions with large losses in crop production, while another 3 billion people will have increased risk of water shortages.
Above the 3C raised level, which may be after 2070, the effects will be catastrophic: the Arctic sea ice will disappear, and species such as polar bears and walruses may disappear with it, while the main prey species of Arctic carnivores, such as wolves, Arctic foxes and the collared lemming, will have gone from 80 per cent of their range, critically endangering predators.
In human terms there is likely to be catastrophe too, with water stress becoming even worse, and whole regions becoming unsuitable for producing food, while there will be substantial impacts on global GDP.